SSR Defined. A solid-state relay is an ON-OFF control
device in which the load current is conducted by one or
more semiconductors – e.g., a power transistor, an SCR,
or a TRIAC. (The SCR and TRIAC are often called
“thyristors,” a term derived by combining thyratron and
transistor, since thyristors are triggered semiconductor
switches.)
Like all relays, the SSR requires relatively low control-
circuit energy to switch the output state from OFF to ON,
or vice versa. Since this control energy is very much lower
than the output power controllable by the relay at full load,
“power gain” in an SSR is substantial–frequently much
higher than in an electromagnetic relay of comparable
output rating. To put it another way, the sensitivity of an
SSR is often significantly higher than that of an EMR of
comparable output rating.
Types of SSR’s. It is convenient to classify SSR’s by the
nature of the input circuit, with particular reference to the
means by which input-output isolation is achieved. Three
major categories are recognized:
• Reed-Relay-Coupled SSR’s (see figure 1), in which the
control signal is applied (directly, or through a
preamplifier) to the coil of a reed relay. The closure of
the reed switch then activates appropriate circuitry that
triggers the thyristor switch. Clearly, the input-output
isolation achieved is that of the reed relay, which is
usually excellent.
• Transformer-Coupled SSR’s (see figure 2), in which
the control signal is applied (through a DC-AC
converter, if it is DC, or directly, if It is AC) to the primary
of a small, low-power transformer, and the secondary
voltage that results from the primary excitation is used
(with or without rectification, amplification, or other
modification) to trigger the thyristor switch. In this type,
the degree of input-output isolation depends on the
design of the transformer.
omega.com
Archive for January, 2009
Solid State Relays SSR
Saturday, January 31st, 2009Simple Telephone Filters
Thursday, January 29th, 2009The telephone lines coming into our homes can carry high-frequency electromagnetic fields , besides the regular speech.This article shows how to set up a simple line filter to lower this unwanted electromagnetic fields.
Why use a phone filter?
Telephone wires run for long distances before they reach a home or office. Along the way they can pick up EMF from other phone lines and electrical wires, especially if they are also carrying high-frequency signals, as is the case with Internet
connections.
Some of these interferences can be heard on the phone, but most are so high a
frequency that they cannot be heard and the phone’s speaker cannot reproduce them. The phone wire coming into the building will act as an antenna and radiate out the high frequency EMF it carries, and so will the telephone itself. For people who are electrically sensitive, this may be a problem, or at least something to avoid.
To find out if there is high-frequency electromagnetic field coming from the phone line, use a simple cheap AM radio. The really cheap models are best for this purpose, as they are notso good at filtering out static, and static is what we are interested in here.A digital radio will not work as well.
Simply turn on the radio, make sure it is set for AM reception, and turn the dial to a place where no stations can be heard and there is very little static. Then put the radio close to the phone cord. When I did that, it sounded like a swarm of angry bees.
A basic ready-to-plug-in filter
A very inexpensive DSL line filter is available from some building supply stores, electronics stores, online, and by mail order (like from Digi-Key, see vendor listing). It costs only about five dollars. It is designed to block DSL-signals, for those who have DSL Internet service (called ADSL in some countries) and only want it on some lines in a house. This filter also dampens other high-frequency noise as well. It is very simple Simple Telephone Filters to use. It just plugs into a phone outlet and then the phone line plugs into it. A variety of styles are available, such as wall mounted filters or filters with extra ports for more than
one phone line.
eiwellspring.org
Electric Power Transmission System
Tuesday, January 27th, 2009In electric power transmission systems, the assets include transmission lines, transformers, power plants and support structures. Maintaining these assets to reliably deliver electric energy at low prices is critical for a nation’s growth and development. Towards this end, we describe a novel service-oriented architecture for sensing, information integration, risk assessment, and decision- making tasks that arise in operating modern high-voltage electric power systems. The proposed framework integrates real-time data acquisition, modeling, and forecasting functionalities provided by relatively autonomous, loosely coupled entities that constitute the power industry to determine operational policies, maintenance schedules and facility reinforcement plans required to ensure reliable operation of power systems.
Modern electric power systems comprising of power transmission and distribution grids consist of a large number of distributed, autonomously managed, capital-intensive assets. Such assets include power plants, transmission lines, transformers, and protection equipment. Over the past 15 years, the investment in acquiring new assets has significantly declined causing many such assets to be operated well beyond their intended life with unavoidable increase in stress on the system. Typically, a single power transmission company has its own centralized control center and is responsible for maintaining different types of equipment. The failure of critical equipment can adversely impact the entire distribution grid and increase the likelihood of additional failures.
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Electrical Power And Energy
Monday, January 26th, 2009Converting Between Mechanical Power And Electrical Power In the SI system there is no difference between electrical and mechanical quantities. Thus power and energy have the units of watts and joules respectively, regardless of whether we are considering mechanical or electrical quantities. In the imperial system the unit of mechanical power is horse power (hp) and these must be converted to watts when considering electrical power. In either case, when converting from mechanical to electrical power or visa versa, efficiencies must be taken into account.
Example
Calculate the power of a lift which can raise a mass of 800kg through a height of 50m in 98.1s.
work done = force × distance
The motor must overcome the force due to the weight (not mass) of the lift. The weight of the lift equals its mass multiplied by the acceleration due to gravity (9.8m/s2).
Calculate the output and input powers of a motor driving the lift if the lift gearing is 80% efficient and the motor is 90% efficient.
The output from the motor must be enough to provide the lift with enough power once the losses in the gears have been taken into account.
input to lift including gears=output of motor=output from gears=4*100=5kw
The electrical power needed to drive the motor must be enough to provide 5kW of power from the motor after the losses incurred while converting electrical power into mechanical power.
Current Differential Protection
Monday, January 26th, 2009Application of Current Differential Protection
to Tapped Transmission Lines
Microprocessor-based current differential relays offer superior protection for power transmission lines. The key advantages over distance relays include better sensitivity for high resistance faults, 100% line protection, and better performance in the single-pole-tripping mode, particularly during evolving and cross-country faults.Besides the well-known requirements of high-speed communication and sampling synchronization, a microprocessor-based differential relay requires ñ as per principle of differential protection ñ that the currents are monitored on all the circuits connected to a protected line including tapped transformers and lines. This may create a problem as the tapped connections are meant to provide a cost-effective alternative to actual substations. The taps are made outside the main substations and may not be equipped with proper protection means such a Circuit Breakers (CBs)
and Current Transformers (CTs). Also, high-speed communication from the tap site may be a problem. This either limits the application of line current differential relays or makes the tapped connections economically less attractive.
This paper discusses application problems and solutions permitting the application of current differential protection to tapped transmission lines without measurements at the tap point
The following sources of differential error signals need to be addressed to make the application possible:
• Total load current of the tapped transformers and lines.
• Faults on the low voltage side of the transformers.
• Magnetizing inrush of the tapped transformers on top of the line capacitive inrush current.
• External ground faults on the high voltage system causing a zero-sequence in feed from the line-side windings of the tapped transformers when connected in a grounded wye.
pm.geindustrial.com
Learn Lathes Machines
Sunday, January 25th, 2009Some important safety precautions to follow when using lathes are:
• Correct dress is important, remove rings and watches, roll sleeves above elbows.
• Always stop the lathe before making adjustments.
• Do not change spindle speeds until the lathe comes to a complete stop.
• Handle sharp cutters, centers, and drills with care.
• Remove chuck keys and wrenches before operating
• Always wear protective eye protection.
• Handle heavy chucks with care and protect the lathe ways with a block of wood
when installing a chuck.
• Know where the emergency stop is before operating the lathe.
• Use pliers or a brush to remove chips and swarf, never your hands.
• Never lean on the lathe.
• Never lay tools directly on the lathe ways. If a separate table is not available, use
a wide board with a cleat on each side to lay on the ways.
• Keep tools overhang as short as possible.
• Never attempt to measure work while it is turning.
• Never file lathe work unless the file has a handle.
• File left-handed if possible.
• Protect the lathe ways when grinding or filing.
• Use two hands when sanding the workpiece. Do not wrap sand paper or emory
cloth around the workpiece
The lathe cutting tool or tool bit must be made of the correct material and ground to the correct angles to machine a workpiece efficiently. The most common tool bit is the general all-purpose bit made of high-speed steel. These tool bits are generally
inexpensive, easy to grind on a bench or pedestal grinder, take lots of abuse and wear, and are strong enough for all-around repair and fabrication. High-speed steel tool bits can handle the high heat that is generated during cutting and are not changed after cooling. These tool bits are used for turning, facing, boring and other lathe operations. Tool bits made from special materials such as carbides, ceramics, diamonds, cast alloys are able to machine workpieces at very high speeds but are brittle and expensive for normal lathe work. High-speed steel tool bits are available in many shapes and sizes to accommodate any lathe operation.
Birla Super Cement
Sunday, January 25th, 2009ENERGY CONSERVATION PLANS AND TARGETS:
The plant improving its energy conservation activities, which requires investments and the management,
has behind the various projects, which will be implemented in the coming years. The lists of major
investment based project are as listed below:
• Installation of S circuit in Cement mill area.
• Installation of ‘Jet Tower Natural Air coolers’ in place of conventional fan blades for cooling tower fan.
• Optimisation of Mill
• Installation of HT VFD for Polycom Fan
• Installation of FRP fan blades for External cooling fan.
• Installation of High Efficiency Dust Collector Fan,
The management is also working on the installation of Captive Power Plant to reduce the energy cost. The
energy forum also looking for energy substitutions available for furthers improvement in this line.
ENVIRONMENT AND SAFETY:
Following are the major Environmental & Safety Activities done at our plant.
• Inclusion of PPC grade Cement to utilize waste fly ash from power plant.
• Atomized handling of fly ash through air tight tankers to avoid fugitive natural escape of fly ash to
environment.
• Pneumatic unloading systems for dust free unloading of fly ash from tankers.
• Installation of additional two dust collectors at W/T to avoid dust emission.
• Installation of gypsum shed of 2*5000 MT to avoid land contamination.
• Development of rain water harvesting reservoir.
• Covering of belt conveyors to avoid dust emission during transportation.
• Construction of BT road inside plant area.
• Development of green plantation by 75%.
• Installations of sprinklers for flower garden & Lawn.
• Concrete flooring for Oil/HSD storage.
• Construction of concrete sewerage treatment plant.
• Installations of one number dust collector at packing plant area.
• Use of sweeping machine to clean the roads & ground floors.
• Charging of bore wells with rain water.
• Development of Flora & Faunas at plant.
energymanagertraining.com
The Hobby of Electronic Circuit Engineering
Saturday, January 17th, 2009Electronic Circuit Engineering Introduction
Electronic Circuit “Beans” Collection
Electronic Circuits Application Garage
Guide to use the PIC
PIC Circuits Gallery
Guide to design of Original LSI(CPLD)
Parts purchase guide
Manufacturing of Original Printed Circuit Board
CAD software EAGLE
Manufacturing of Original Plastic Case
3D photograph collection
Java Programming
Search Engine Collection
Cool Links
Data Sheets Collection
Webcams Collection
Homepage Production Room
Access Ranking
www.interq.or.jp
Electronic Circuit Engineering Introduction
Saturday, January 17th, 2009Basic knowledge of Electronic parts
Basic knowledge of Engineering Instruments
Introduction of Engineering Method
Assembly process
Differentiation circuit
Integration circuit
Simple amplifier
555 timer
555 oscillator
A-stable multivibrator (IC type)
A-stable multivibrator (TR type)
DC/AC inverter (1)
DC/AC inverter (2)
+12V/-12V Power supply unit
+/-12V -> +/-5V Power unit
+30V power supply with +5V
+30V DC-DC converter
Switching regulator (1)
Switching regulator (2)
Electric power controller
Thermostat
LCD thermometer
Square wave oscillator (1)
Square wave oscillator (2)
Triangular wave oscillator
Sawtooth wave oscillator
Sine wave oscillator
Sine/Cosine wave oscillator
LED counter
Frequency induction switch
Digital dial
PLL synthesizing oscillator (1)
PLL synthesizing oscillator (2)
PLL synthesizing oscillator (3)
www.interq.or.jp1
www.interq.or.jp2
Electrical Circuits
Friday, January 16th, 2009This file Will tell you what is a circuit? ,electronic circuits,and example of a simple circuit,circuits and conductors,parallel circuits,electric current,and all fundamentals of electric circuits,Current, Resistance & Power ,direct current circuits with batteries and resistors Capacitors are commonly found in electric circuits. A circuit containing capacitors and resistors together is called an RC circuit.
www.ucopenaccess.org
www.ncsu.edu
www.didaktik.itn.liu.se